For the purpose of introducing a catheter into a blood system for angiography, conventionally a guide wire has been used to more safely and more accurately carry out the introduction. The guide wire is effective in situations involving relatively thick blood vessels or those having relatively simple branches or bending in a relatively simple form. It is, however, very difficult to carry the catheter into a depth of a blood vessel branching very minutely, such as a coronary of a human heart and especially for substantially stenosed portions thereof, and a guide wire based on a completely different concept is required. Especially in the case of guide wire used for a catheter for blood vessels forming in substantially stenosed sections, it is essential that a portion near a tip of the guide wire should be opaque against radioactive rays, such as X-rays, in order to accurately detect a stenosed portion. To achieve the object as described above, a guide wire as disclosed, for instance, in Japanese Patent Publication No. 25024/1992 has been proposed.
In the conventional type of guide wire as described above, two pieces of coil are connected to a section near a tip of shaft made of metal having a high twistability, and of the two pieces of coil, the one closer to the tip is made of a radiopaque material so that the guide wire will be provided with high flexibility and high bending capability as well as be easily detected by radioactive rays, through various devices which are introduced. However, in this type of guide wire, two coils made of different materials are artificially coupled and connected by means of screwing or soldering, so particular considerations are required to maintain mechanical safety and strength in the connected section, and in addition, because mechanical characteristics of the connected section become discontinuing when a guide wire passes through a blood vessel having an extremely small curvature, sometimes passage also becomes impossible due to discontinuity of bending radius in this connected section. Namely in FIG. 1A and FIG. 1B, each diagrammatically illustrating the situations where the problem as described occurs, if the connected section 51 of the guide wire 50 is too hard, it can not follow bending of a blood vessel 52 and can not pass through the section (FIG. 1A), and, on the other hand, if the connected section 51 is too soft, it bends and passage becomes impossible (FIG. 1B).